1. Field of the Invention
Embodiments disclosed herein generally relate to a magnetic read head for use in a hard disk drive.
2. Description of the Related Art
The heart of a computer is a magnetic disk drive which typically includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and/or write heads over selected circular tracks on the rotating disk. The suspension arm biases the slider towards the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent to a media facing surface (MFS), such as an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing, the write and read heads are employed for writing magnetic transitions corresponding to host data. The read and write heads are connected to a signal processing circuitry that operates according to a computer program to implement the writing and reading functions.
Decreasing the size of devices has necessitated the reduction in the space available for hard disk drives while at the same the requirements for larger capacity disk drives have continued to grow. As the capacities of disk drives grow, the areal recording density has increased to provide a greater volume of data to be stored in the same physical space. Increasing the areal recording density of next generation heads requires shrinking the size of the corresponding read and increasing the signal to noise ratio of the read head.
However, increasing the signal to noise ratio of the read head necessitates the reduction of the resistance-area RA product while keeping the magnetoresistance ratio high in a small RA region. For tunnel junction devices, the magnetic field interlayer coupling (Hint) increases in a positive direction exponentially with the decrease in the resistance area (RA) of the barrier tunnel junction. This is due to magnetostatic coupling inherent to thin barrier tunnel junctions. Since the interlayer coupling field biases the free layer in the pinned layer direction, attaining a stable longitudinal bias state relative to the ABS requires a large stabilization field (from hard or soft bias layers) which increases the stiffness of the sensor and decreases its signal output.
Conventionally, this control is provided by increasing the hard/soft bias field acting on the free layer, which reduces the sensitivity of the sensor. Currently, there are no known efficient means for providing a means to reduce the Hint while still maintaining the low RA and the high magnetoresistance ratio needed in the higher areal recording densities of next generation devices.
Therefore there is a need in the art for a magnetic read head with a small Hint, for the use with increased areal recording densities.